Network Working Group J. Winett
Request for Comments: 110 MIT Lincoln Laboratory
NIC: 5809 25 March 1971
Conventions for Using an IBM 2741 Terminal as a User Console forAccess to Network Server Hosts
Disclaimer
This material has not been reviewed for public release and is
intended only for use with the ARPA network. It should not be quoted
or cited in any publication not related to the ARPA network.
TO: NIC
FROM: Joel M. Winnet (LL)
SUBJECT: Conventions for Using an IBM 2741 Terminal as a User
Console for Access to Network Server Hosts
An IBM terminal can be used to key in 92 different codes. These
include 88 graphics plus the 4 controls SP, BS, HT, and NL. Each of
these have defined ASCII codes except the cent graphic ([1]) and the
New Line Control (NL). When the NL character is keyed, the program
receiving the keyboard input can translate this signal into the
appropriate line end signal for the host which is being used. That
is, to a NL, CR, or LF code whichever is appropriate. There are 7
other ASCII graphic characters ( {, }, [, ], ^, \, `) and 31 other
ASCII controls which cannot be keyed on a 2741 terminal. A
convention must be established so that all 128 ASCII codes can be
keyed from a 2741 terminal. This requires that one character be
chosen as an escape (or prefix) character which,a together with
following characters, can be converted into any desired ASCII code.
In addition to this escape character, there are three other functions
which are usually indicated by the typing of a single character key.
These are:
a) character delete -- to cause this character and the preceding
character in the input line to be deleted.
b) line delete -- to cause this character and all previous
characters in the current input line to be deleted.
c) logical line end -- to cause all characters keyed after the
last logical line end character or last NL character up to this
character to be considered as one logical line with this
character being treated as if the NL key were entered.
Characters following the logical line end character up to
another logical line end character or a NL character are used
for form another input line.
Winett [Page 1]

RFC 110 Conventions for Using an IBM 2741 25 March 1971
Since characters keyed are normally sent to the Server Host, a method
must be defined to allow characters keyed to be interpreted by the
user program. A system escape character can be used for this
purpose. On character at a time systems, the characters keyed
between two system escape characters can be interpreted by the user
program. On line at a time systems, characters keyed after the
system escape character and up to and including a NL character can be
interpreted by the user program. Lines interpreted by the user
program are not sent to the Server Host.
For those host systems which require use of the INS or INR network
control commands, a method must be defined for causing these commands
to be sent. These can be sent on a command to the user program
either after keying the system escape character or through the use of
the 'attention' button on a 2741 terminal. This choice will depend
on the characteristics of the terminal user's operating system.
Other commands to the user program might be to:
a) suppress typeout of received messages
b) restore typeout of received messages
c) direct received message to a disk file
d) direct keyed input to a disk file
e) abort the user program
The following characters are recommended for the special functions
listed above:
1. character escape $NOT [1]
2. system escape |
3. character delete @
4. line delete $CENT [1]
5. logical linend #
For the 7 ASCII graphics not on a 2741 terminal, the following
character escape and graphic pairs are recommended:
$NOT < to translate to [
$NOT > to translate to ]
$NOT ( to translate to {
$NOT ) to translate to }
$NOT " to translate to ^
$NOT / to translate to \
$NOT ' to translate to `
Winett [Page 2]

RFC 110 Conventions for Using an IBM 2741 25 March 1971
To permit the special function characters to be keyed, the following
character escape and graphic pairs are recommended:
$NOT - to translate to $NOT
$NOT : to translate to |
$NOT , to translate to @
$NOT . to translate to $CENT
$NOT = to translate to #
To key in the ASCII control codes, it is recommended that the
character escape followed by two letters be used to specify a control
code. These two letters are derived from the mnemonic name of the
ASCII control function and are as follows:
$NOT AC to translate to ACK X'06'
$NOT BE to translate to BEL X'07'
$NOT BS to translate to BS X'08'
$NOT CA to translate to CAN X'18'
$NOT CR to translate to CR X'0D'
$NOT D1 to translate to DC1 X'11'
$NOT D2 to translate to DC2 X'12'
$NOT D3 to translate to DC3 X'13'
$NOT D4 to translate to DC4 X'14'
$NOT DE to translate to DEL X'7F'
$NOT DL to translate to DLE X'10'
$NOT EM to translate to EM X'19'
$NOT EN to translate to ENQ X'05'
$NOT EO to translate to EOT X'04'
$NOT ES to translate to ESC X'1B'
$NOT EB to translate to ETB X'17'
$NOT EX to translate to ETX X'03'
$NOT FF to translate to FF X'0C'
$NOT FS to translate to FS X'1C'
$NOT GS to translate to GS X'1D'
$NOT HT to translate to HT X'09'
$NOT LF to translate to LF X'0A'
$NOT NA to translate to NAK X'15'
$NOT NU to translate to NUL X'00'
$NOT RS to translate to RS X'1E'
$NOT SI to translate to SI X'0F'
$NOT SO to translate to SO X'0E'
$NOT SH to translate to SOH X'01'
$NOT SP to translate to SP X'20'
$NOT ST to translate to STX X'02'
$NOT SU to translate to SUB X'1A'
$NOT SY to translate to SYN X'16
$NOT US to translate to US X'1F'
$NOT VT to translate to VT X'0B'
Winett [Page 3]

RFC 110 Conventions for Using an IBM 2741 25 March 1971
Note that the controls SP, BS, and HT can be specified using the
character escape character or directly by keying the appropriate key
on a 2741 terminal.
Endnote
[1] The following identifiers are substituted for graphics not in
ASCII:
$CENT Cent sign
$NOT Logical NOT ("bent bar")
See the PDF version of this document for graphics that cannot be
represented in ASCII format.
[This RFC was put into machine readable form for entry]
[into the online RFC archives by Lorrie Shiota, 10/02]
Winett [Page 4]